The present invention is generally related to water softeners, and, more particularly, to system and techniques for the filtration and reuse of spent brine, such as may be produced during the regeneration of salt-based ion-exchange water softening systems.
Residential water softeners typically use cation exchange resins, which remove ions, such as calcium and magnesium ions, which commonly contribute to the hardness of water. During the ion exchange process, the resin releases a cation, e.g., a divalent cation, into the softened water. Periodically, preferably when the resin bed becomes saturated with the divalent cations, the resin is regenerated by flushing it with a concentrated regenerant aqueous solution, such as salt (e.g., sodium chloride) brine. In the process, the cations producing hardness (calcium and magnesium, for instance) are released into the regeneration stream that is disposed of into the municipal sewer system.
Unfortunately, excess sodium chloride from the regenerant brine solution is also discarded to the sewer system. Because many municipalities nowadays treat sewer water for agricultural irrigation or other purposes, discharge of brine is often no longer acceptable because the discharged brine would introduce excessive salinity to the agricultural fields and present environmental pollution of the ponds and nearby lands being irrigated. As a consequence, many municipalities may enact regulations effectively banning the discharge of brine from the regeneration of residential water softeners.
In addition, residential users must periodically buy pelletized salt in heavy bags and carry them to the location of the ion exchange softener, which is often not easily accessible.